A Chinese who bought two sculptures owned by the late fashion designer Yves Saint Laurent at a controversial auction has said he will not pay for the treasures, which were looted from a Beijing palace during the opium wars.

The relics were sold in Paris last week, to the anger of many in China. The telephone bidder paid €31m (£27m) for the two bronzes.

While a French court ruled that the auction was legal, Beijing argued that the sculptures should be returned to China.

Today, the argument took a fresh twist as Cai Mingchao, an adviser to a Chinese foundation which seeks to retrieve plundered treasures, told a news conference that he was the collector who won the auction.

"What I need to stress is that this money cannot be paid," he added, describing his bid as a patriotic act.

"I think any Chinese person would have stood up at that moment. It was just that the opportunity came to me. I was merely fulfulling my responsibilities."

Christie's had no immediate comment and could not confirm Cai as the bidder, the spokeswoman Yvonne So told the Associated Press.

She said that if a bidder couldn't or wouldn't pay, Christie's usually worked with the buyer and vendor to find a solution. The auction house said the legal ownership of the pieces had been clearly confirmed, a view upheld by French courts.

Wang Weiming, one of the heads of China's Lost Cultural Relics Recovery Programme – the foundation which Cai advises – said she was "not sure" if or when the bronzes would return to China.

"These national treasures are probably still in France," Wang told Reuters. "We'll have to see how the situation develops."

The rabbit and rat heads were part of an elaborate fountain which stood in the Yuanmingyuan, the imperial summer residence, until it was razed and looted by French and British troops in 1860.

The destruction of the Old Summer Palace still rankles and Pierre Bergé – Saint Laurent's partner and co-owner of a vast art collection – further upset Chinese patriots when he offered to return the relics without charge if China would "give the Tibetans back their freedom".

One Chinese expert said the objects were overpriced. Luo Zhewen, the honorary chairman of the Cultural Artefact Association, told Shanghai's Oriental Morning Post that the two heads were worth less than 1m yuan (£103,000). "More than that, and the buyer should figure that he's been cheated."

He claimed their real value was as "criminal evidence" of the destruction of the palace, saying that they were coarsely made compared with other imperial artefacts.

"These days, they can be easily manufactured at small factories in Beijing or Guangzhou," he said.

Five of the other fountain heads have been bought by Chinese business figures and repatriated, while experts fear the other five may have been destroyed.

Christie's three-day sale of Saint Laurent's art collection earned a total of more than €373m .